For example, an idle-stop controller is disclosed in Patent Document 1 (JP-A-2004-156589). The controller includes a switching element directly fixed to a substantially disk-shaped heat sink and a circuit board having a printed wiring layer fixed on the heat sink, and includes a control IC or the like on the circuit board. The heat sink is provided with double side frames on the entire outer periphery and the entire inner periphery attached thereto, and is fixed to an outer wall at the rear end of a bracket via the outer peripheral side frames. Resin is injected into a ring-shaped recess surrounded by the inner and outer peripheral frames of the heat sink, whereby the switching element, the circuit board and the control IC or the like are protected from salty mud water or the like.
The controller has a cooling structure in which a resin cover is fixed to the bracket so as to cover the heat sink, so that cooling air flowing from an air-intake hole provided on the resin cover flows into the bracket while cooling the heat sink, and cools a stator winding and a rotor winding, and then flows out from the bracket.
Patent Document 1: JP-A-2004-156589 (see FIG. 9 to FIG. 11, Paragraphs [0068] to [0072])